The present invention relates to a lighting control apparatus of a control panel in an automobile, and it can be applied, for example, to a control panel of an automobile air-conditioning system.
The Japanese Patent Laid Open Publication No. 4-143134 discloses an apparatus for controlling a luminosity of a control panel of an air-conditioning system and a radio/stereo set in three steps according to a brightness/darkness outside a car-room. This apparatus has lighting means for lighting the control panel for the air-conditioning system and the radio/stereo set, brightness reduction means for decreasing a luminosity of the lighting means, and brightness reduction control means for controlling the brightness reduction means in three steps according to a luminosity outside the car-room. The brightness reduction means is driven when a light switch is turned on. The brightness control means has a day mode, a night mode and a medium mode to be an intermediate of these two modes. The brightness reduction control means selects one of the day, night and medium modes based on an output of a sun sensor for detecting a quantity of solar radiation, and gives the selected mode to the brightness reduction means. If the selected mode is the day mode, the brightness reduction means does not reduce the luminosity of the lighting means. If the selected mode is the night mode, the brightness reduction means reduces the luminosity of the lighting means to a normal brightness reduction condition. If the selected mode is the medium mode, the brightness reduction means reduces the luminosity of the lighting means to a luminosity between the day and night modes.
According to the above-mentioned prior art, the luminosity of the control panel of the air-conditioning system and the radio/stereo set is merely controlled according to the brightness/darkness outside the car-room. Hence, the prior art cannot set the luminosity of the control panel to a luminosity which a driver wants in conjunction with a luminosity of an instrument panel that provides a speedometer and a tachometer. The luminosity of the control panel of the air-conditioning system and the radio/stereo set varies by a difference between a lighting element of the instrument panel and that of the control panel, and, by a difference of secular change between the instrument panel's lighting element and the control panel's lighting element, in relation to the luminosity of the instrument panel. Since the prior art cannot set the luminosity of the control panel as desired by the driver, when the luminosity of the control panel is too dark/bright relative to the luminosity of the instrument panel, it cannot adjust the luminosity of the control panel brighter/darker.